The individual sections of sectionalized rotor blades are either individually attached to a spar or they are individually stuck onto the spar and then clamped together as a unit, see German Patent Publication (DE-AS) No. 1,406,443 or French Pat. No. 888,216. These rotor blades are constructed for helicopters, and this prior art aims for a simple production and high elasticity of the rotor blades.
Recently, attempts have been made to produce electricity using wind powered devices. One possibility is to erect a high mast at a prevalently windy location, which mast has a winged rotor with, for example, two rotor blades or wings. The wind driven rotor then drives an electric generator. Some of these blades of such rotors have a length of up to 60 meters and hence, depending on the material used, they weigh up to 20 tons. Known construction principles may only be applied to rotor blades of such dimensions to a limited extent, even if only for the fact that different criteria regarding the elasticity or regarding the strength are given for rotating blades of helicopters or for wind driven devices. Problems in construction, assembly, and operation result for wind driven devices because of the size of the rotor blades.
It has been suggested to manufacture such rotor blades as a single piece using fiber reinforced synthetic materials, since these materials offer advantages with reference to weight and strength. In order to manufacture a rotor blade in this manner, at least a specially built production bench approximately 60 meters long and equally long autoclaves would be necessary, in which the finished rotor blades would be heat cured at temperatures between 100.degree. C. and 250.degree. C.
The transporting and the assembling of such one piece rotor blades or rotor wings of this type is also complicated, simply because of the great length. The rotor blades may have to be mounted on the mast under windy conditions. Accordingly, the wind forces have to be controlled by means of appropriate assembly aids or facilities.
If the construction principle mentioned above for helicopter rotor blades comprising individual sections is used, then the construction of these individual sections may be made easier. However, the assembling of the individual sections on the blade spar which is generally made of tubular steel, the transporting of the finished rotor blade and the mounting of the finished rotor blade on the mast remain complicated.
Finally, a rotor wing of a wind driven device in operation is subjected to extremely high loads. Accordingly, the blade tips of the rotor for example, attain speeds of up to 150 meters per second, the resulting centrifugal forces and also the torsional forces must be taken up completely by the blade material.